They extend from the beginnings of his career, with opus 2, to close to the end, with opus 111. The sonatas of Haydn and Mozart, Beethoven's immediate predecessors, were largely written for the enjoyment of amateurs, but most of the Beethoven sonatas require considerable skill and some are at the limits of virtuosity. While it would be generally acknowledged that the Beethoven sonatas surpass considerably those of Haydn and Mozart, I doubt that any written for piano since surpass Beethoven's. Here is the Wikipedia guide to the sonatas. Let's take a look at three and, as is traditional with Beethoven, make them an early, a middle and a late period sonata.
Here's the first movement of the fairly early Sonata Pathétique, played by Claudio Arrau:
If it weren't for the more coherent harmonic structure, you might almost think you were listening to Liszt during that opening Grave. Beethoven was only 27 when he wrote this and already it is unmistakable. The Grave returns--twice! And when the allegro arrives, the drive, the intense focus on a small amount of thematic material--these are characteristics of all his music. After this comes a melting slow movement with one of those themes whose utter simplicity astounds every time you hear it. It takes great artistry to write a movement like this:
That was Artur Schnabel, the first great Beethoven specialist of the era of recording. I sincerely hope you weren't eating a ham sandwich while that was playing. Schnabel put off recording Beethoven for many years because he said he was afraid that if he released recordings of the Beethoven sonatas someone, somewhere, would be listening to them while eating a ham sandwich. For the last movement, a rondo, let's go to Berlin where, in 2005, Daniel Barenboim performed the complete Beethoven piano sonatas over 8 concerts in 2 weeks at the Staatsoper. They are available on six DVDs.
Tomorrow a middle-period sonata...